EP1957781A1

EP1957781A1 - Method for controlling a fuel injector on a diesel engine

Info

Publication number: EP1957781A1
Application number: EP06807393A
Authority: EP
Inventors: Stefan Polach; Dara Torkzadeh
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2005-12-02
Filing date: 2006-10-19
Publication date: 2008-08-20
Anticipated expiration: 2026-10-19
Also published as: WO2007062914A1; DE102005057571A1; EP1957781B1; US20100042309A1; US8571784B2; DE502006004035D1; JP2009517591A; JP4755695B2

Abstract

A method for controlling a fuel injector on a diesel engine (10) is disclosed with a given control duration from a control start time, wherein a set value (BB_soll) for combustion start of a combustion chamber content in the diesel engine (10) is determined. The invention is characterised in that an ignition delay (ZV), between the start of control and the start of combustion is estimated from operating parameters of the diesel engine (10) with a computational model (52) and the control start is generated from the set value (BB_soll) for the start of combustion and the estimated ignition delay (ZV). A controller (30) is also disclosed, which controls the method operation.

Description

description

title

Method for controlling a fuel injector of a diesel engine

State of the art

The invention relates to a method for controlling a fuel injector of a diesel engine with a predetermined drive time from a start of control, wherein a desired value for a start of combustion of a

Combustion chamber filling of the diesel engine is determined. The invention also relates to a control device which controls the sequence of such a method.

Such a method and such a control unit is known from DE 195 36 110 Al. In the known method, the desired value is determined from measured operating parameters of the diesel engine, an actual value is determined from signals of various sensors, and the actual value is regulated to the desired value in a closed control loop. The manipulated variable for the control is the beginning of a signal with which the injector is triggered to trigger an injection. The beginning of this signal is in

Also referred to below as the start of control.

Base values for the start of control are stored, for example, in a map, which is addressed by operating parameters of the diesel engine. Between the start of the drive and the start of burning is the so-called Start delay or dead time of the injector and the so-called ignition delay. The pull-in delay is due to the design of the injector and corresponds to a delay with which the injector responds to the drive signal with the beginning of an injection. The ignition delay is between this injection start and an actual start of combustion, ie the start of combustion. The start of combustion is known in the diesel engine triggered by a self-ignition of the fuel, which is injected into the heated by compression combustion chamber filling.

These influences can be used when determining the map values or by

Correction of the values read out. The correction can be effected by a control intervention or by linking with operating parameter-dependent determined correction values.

It has been found that in the known methods and there especially at operating point changes a non-circular engine running occurred.

On the other hand, the method according to the invention is characterized in that an ignition delay, which lies between the control start and the start of combustion, is estimated from operating parameters of the diesel engine with a computer model and the start of control is formed from the setpoint for the start of combustion and the estimated ignition delay. The control unit according to the invention is characterized in that it controls the sequence of such a method.

Advantages of the invention

An estimate of the ignition delay with a calculation model that processes operating parameters of the diesel engine results in an overall approximation of the actual value of the start of combustion to its setpoint. For a diesel engine that operates without regulation of the start of combustion, This results in an improved smoothness and a more efficient engine operation in a wide range of operating conditions and transitions between operating conditions. In diesel engines with a control of the start of combustion, there is a significant improvement in smoothness in the transition between different operating points and / or

Combustion method, since the base values for the start of control, which should lead to a specific start of combustion, are linked to an immediately effective ignition delay correction.

On the other hand, the correction of a structure which works in addition to setpoint values for a start of control has disadvantages: if it reacts quickly, overshoots can occur in unsteady operation, which also have a negative effect on the operating behavior of the diesel engine. On the other hand, if the overshoots are avoided, the control works too slowly to effectively compensate for mismatches in rapid point-to-point changes.

In order to be able to control the start of combustion even better in stationary operating states, the method is preferably combined with a control of the start of combustion.

To meet future emission standards, it will be necessary to operate diesel engines in different operating ranges with different combustion processes. In particular, between a lean operation with stratified and thus inhomogeneous fuel distribution in

Combustion chamber and a homogeneous operation with a more homogeneous fuel distribution distinguished. The more homogeneous fuel distribution is achieved at least in part by an increased ignition delay. The increased ignition delay is generated by a high exhaust gas recirculation rate and thus by an increased inert gas content at the combustion chamber filling. At sufficiently high exhaust gas recirculation rates, interactions between different influences on the ignition delay occur. Thus, the influence of an increased combustion chamber filling, which would rather reduce the ignition delay, is changed by the inert gas component resulting from the exhaust gas recirculation. At the same time, the temperature influence of the recirculated exhaust gases changes the temperature of the combustion chamber filling. It is therefore particularly preferred that the ignition delay is estimated using a physical model that simulates coupled influences of at least two operating parameters of the diesel engine.

Further advantages will become apparent from the description and the accompanying figures.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

drawings

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. It show, each in schematic form

Fig. 1 shows the technical environment of the invention;

Fig. 2 shows a first embodiment of an inventive

Method for setting the start of burning by an open

Timing chain; and FIG. 3 shows a second embodiment of a device according to the invention Method for setting the start of combustion in a closed loop.

Description of the embodiments

In detail, FIG. 1 shows a diesel engine 10 with at least one combustion chamber 12, which is movably sealed by a piston 14. The combustion chamber 12 is filled via an inlet valve 16 with air from a suction pipe 18. Burned gases are expelled via an exhaust valve 20. For compressed in the compression stroke combustion chamber filling 22 fuel from a fuel pressure accumulator 24 is injected via an injector. Further, the combustion chamber 12 exhaust gas is supplied via an exhaust gas recirculation valve 26 in an exhaust gas recirculation 28. The injector 22 and the exhaust gas recirculation valve 26 are controlled by a control unit 30, which processes signals from various sensors. In the illustration of FIG. 1, these are

Combustion feature sensors 32 and / or 34, a fuel pressure sensor 36, an angle sensor 38 on a component 40 which rotates in synchronism with operating cycles of the diesel engine 10, a driver desire 42, a temperature sensor 44 and an air mass meter 46th

The component 40 is, for example, a flywheel rotatably connected to a crankshaft of the diesel engine 10. However, it may be connected in another embodiment, for example, with a camshaft of the diesel engine 10. It is understood that real diesel engines 10 may have other sensors, such as exhaust gas temperature sensors. Furthermore, not every diesel engine 10 has to have all the sensors 32 to 46. For example, control of the start of combustion may be based on the signal from only one combustion feature sensor 32 or 34. The other sensor is then not necessary. When setting the start of control in an open timing chain can be on both Combustion feature sensors 32, 34 are dispensed with. The air mass meter 46 is also not mandatory.

Essential for an understanding of the invention, however, is that the control unit 30 from the supplied sensor signals drive signals in the form of pulse widths ti for injections, is metered with the fuel for combustion in the combustion chamber 12, and outputs in the form of signals S_agr for controlling the exhaust gas recirculation valve 26 ,

The combustion feature sensor 34 is a

Combustion chamber pressure sensor, which delivers a combustion chamber pressure p_br, while it is the alternative or complementary existing combustion feature sensor 32 is a structure-borne noise sensor, which delivers a structure-borne noise signal KS. The fuel pressure sensor 36 signals the fuel pressure or injection pressure p_kr. The angle sensor 38 provides in the embodiment of Fig. 1, a crankshaft angle information ⁰ KW as information about the position of the piston 14 in his work cycle. It is understood that this information can be derived not only from the crankshaft angle information, but also, for example, from a camshaft angle information. From the angle signal ⁰ KW can still information about the speed n of

Diesel engines are derived. The driver's request FW represents a measure of a torque request by the driver and is detected, for example, as the accelerator pedal position by the driver's request generator 42. An engine temperature T is provided by the temperature sensor 44. The air mass meter 46 provides a measure of the flowing into the combustion chamber 12

Air mass ml.

Fig. 2 shows a first embodiment of a method for adjusting the start of combustion. In this embodiment, the start of combustion is set with an open timing chain. The dashed line 48 separates functions of Control unit 30 of functions of the diesel engine 10. First, in block 50, a determination of a desired value BB_setpoint for the start of combustion is made, which is to be triggered with the next injection. The determination takes place as a function of signals present in the control unit 30, in particular as a function of the rotational speed n and a

Torque request, as specified by the driver's request FW.

In diesel engines, which are operated in different operating modes such as a lean operation with stratified fuel distribution or a homogeneous operation with more homogeneous fuel distribution in the combustion chamber 12, the specification of the start of combustion setpoint BB_soll additionally takes place in dependence on a signal BA, which indicates the operating mode. The default can be done by accessing a stored in the control unit 30 map, which is addressed by the above sizes and possibly other sizes. As a further variable comes, for example, a torque command input in question, which is generated independently of the driver's request FW in the control unit 30. Such torque request specifications serve, for example, to support switching operations in automatic transmissions. Another example of a further variable is a signal that provides a desired efficiency degradation for heating

Exhaust aftertreatment components over a late shift of the start of combustion and thus the focal point of combustion causes.

The desired value BB_soll output by the block 50 is corrected by a calculation model for the ignition delay, which is represented by the block 52 and which is also referred to below as the ignition delay model. The ignition delay model 52 simulates the ignition delay based on operating parameters that characterize the condition of the combustion chamber charge before and during injection. Essential state variables in this context are the gas mass enclosed in the combustion chamber, Oxygen content and its temperature. In this case, the ignition delay model reduces the modeled ignition delay with increasing combustion chamber charge (gas mass), increasing oxygen content, decreasing droplet size of the injected fuel and increasing temperature of the combustion chamber charge and thus simulates the behavior of the actual ignition delay.

The combustion chamber filling is essentially due to the air sucked in on a suction stroke of the piston 14 and the amount of exhaust gas recirculated into a combustion chamber filling. The mass of sucked air results as a function of the signal ml of the air mass meter 46 and the rotational speed n. Analogously, the recirculated exhaust gas mass in a combustion chamber filling by the exhaust gas recirculation controlling signal S_agr and the rotational speed n can be determined.

The temperature is significantly influenced by the heat of compression and heat transfer from Brennraumwandungen to the combustion chamber filling. The heat of compression depends on the combustion chamber filling and the temperature effect of the heat transfer depends on the temperature T of the diesel engine 10. The droplet size depends on the injection pressure p_kr.

There are interactions between the individual influencing factors. Thus, a high exhaust gas recirculation rate with a smaller fresh air mass in the combustion chamber has a greater effect than with a larger fresh air mass. The effect of exhaust gas recirculation on the combustion chamber temperature also depends on the mass of fresh air in the combustion chamber. In a particularly preferred embodiment, the ignition delay is estimated using a mathematical model that simulates coupled influences of at least two operating parameters of the diesel engine. It is further preferred that one of the at least two operating parameters is an exhaust gas recirculation rate. As already mentioned, the exhaust gas recirculation rate in particular affects the combustion chamber charge and / or the temperature the combustion chamber filling. Because of the coupled influences of these parameters, the combustion chamber charge and / or the temperature is preferably used as a second or further parameter in modeling. In one embodiment, an inert gas fraction resulting from the exhaust gas recirculation at a combustion chamber filling is estimated in the estimation of an influence of the

Combustion chamber filling at the ignition delay considered. Alternatively or additionally, a temperature increase of the combustion chamber filling resulting from the exhaust gas recirculation rate is taken into account in the estimation of an influence of the temperature of the combustion chamber filling.

An ignition delay formed with the ignition delay model 52 is subtracted from the setpoint for the start of combustion from the block 50. In the functional structure of FIG. 2, the subtraction takes place in the linkage 56. If a zero is assigned to the top dead center OT of the piston 14 in the compression stroke as a fixed angular position, then the nominal values for the start of combustion, which are generally before top dead center, have a negative one Sign. By subtracting the amount of ignition delay formed in the linkage 56, a desired value for the start of injection is thus formed, which is earlier in time than the nominal value for the start of combustion.

From this setpoint for the start of injection, a pull-in delay or injector dead time IT, which elapses between a triggering of the injector and an actual opening of a flow cross section in the injector 22, is also subtracted. This Injektortototzeit can, for example, the battery voltage and / or supply voltage u and the

Depend on fuel pressure p_kr, with the aid of injection pulse widths are formed for an injector 22. In the illustration of FIG. 2, such an injector dead time is formed in the block 58 and subtracted in the link 60 from the setpoint for the start of injection. The result of the link 60 is the actual start of control, starting from which an injector 22 with an opening Injection pulse width ti must be controlled in order to realize a desired start of combustion after an actually occurring ignition delay ZV. In the illustration of FIG. 2, the block 62 represents the actual ignition delay ZV and the block 64 represents the actual start of combustion and thus an actual value BBJst of the start of combustion.

Fig. 2 thus represents a formation of a control start for an injector 22, which takes place in an open control chain and which is based on the specification of a setpoint for the start of combustion, from which a drive start is formed with the aid of a calculation model for the ignition delay. Alternatively, the

Ansteuerbeginn also be formed and corrected in a closed loop. Such a control loop is shown in FIG. The object of Fig. 3 differs from the object of Fig. 2 by the elements 66, 68 and 70. Like reference numerals designate like objects. In the link 66, a control deviation is formed from the setpoint for the start of combustion and an actual value for the start of combustion. The actual value BBJst is determined by processing the signals from one or both of the combustion feature sensors 32, 34. A controller 68 processes the control deviation to a control variable, which is linked in the embodiment of FIG. 3 in a link 70 with the setpoint for the start of combustion. It will be appreciated that the link 70 may also be between the links 56 and 60 or between the link 60 and the block 62.

Claims

claims

1. A method for controlling a fuel injector (22) of a diesel engine (10) with a predetermined drive time starting from a Ansteubeg, wherein a setpoint (BB_soll) for a start of combustion of a combustion chamber filling of the diesel engine (10) is determined, characterized in that an ignition delay (ZV), which lies between the actuation start and the start of combustion, is estimated from operating parameters (s_gr, p_kr, T, n, ml) of the diesel engine (10) with a calculation model (52) and the actuation start is based on the desired value (ZV). BB_soll) for the start of combustion and the estimated ignition delay (ZV) is formed.

2. The method according to claim 1, characterized in that actual values (BBJst) of the start of combustion are determined and set in a closed control loop to setpoints (BB_soll).

3. The method according to claim 1 or 2, characterized in that the

Ignition delay (ZV) with a computational model (52) is estimated that mimics coupled influences of at least two operating parameters (s_agr, p_kr, T, n, ml) of the diesel engine (10).

4. The method according to claim 3, characterized in that one of the at least two operating parameters (s_gr, p_kr, T, n, ml) is an exhaust gas recirculation rate (s_agr).

5. The method according to claim 4, characterized by a combustion chamber filling and / or a temperature (T) of the combustion chamber filling as a parameter.

6. The method according to claim 4, characterized in that a resulting from the exhaust gas recirculation inert gas content is taken into account at a combustion chamber filling in the estimation of an influence of the combustion chamber filling at the ignition delay.

7. The method according to any one of claims 4 to 6, characterized in that a resulting from the exhaust gas recirculation rate increase in temperature of the combustion chamber filling is taken into account in the estimation of an influence of the temperature of the combustion chamber charge.

8. Control unit (30) which controls a fuel injector (22) of a diesel engine (10) with a predetermined drive time from a control start and to a setpoint (BB_soll) for a start of combustion of a combustion chamber filling of the diesel engine (10), characterized in that the control unit (30) estimates an ignition delay (ZV), which lies between the activation start and the start of combustion, from operating parameters (s_gr, p_kr, T, n, ml) of the diesel engine (10) and

Start of control from the setpoint (BB_soll) for the start of combustion and the estimated ignition delay forms.

9. Control unit (30) according to claim 9, characterized in that it controls a sequence of at least one of the methods according to claims 2 to 8.